[RodB]

Hello Steve and welcome to the Phorum. Your 37-620J uses a 10-1/2 inch HS speaker. The 38-620 uses an 8 inch S7 speaker. You can find a replacement that has an output transformer that matches your singleended 6K6 output tube. Other Philcos that use this speaker are 37-610J, 37-2620J, 38-8X, 38-9K, 38-9X, 38-10F. If you find a non-Philco speaker/OPT that's suitable, you may have to rewire it to make it function.